Left-handed color-sextet diquark in the kaon system

Chuan Hung Chen, Takaaki Nomura

Research output: Contribution to journalArticle

Abstract

We investigate whether a color-sextet scalar diquark (H6) coupling to the left-handed quarks contributes to the ΔS=2 process. It is found that the box diagrams mediated by W and H6 bosons have no contributions to ΔS=2 when the limit of mt=0 is used, and the flavor mixing matrices for diagonalizing quark mass matrices are introduced at the same time. When the heavy top-quark mass effects are taken into account, it is found that in addition to the W-H6 box diagrams significantly contributing to ΔS=2, their effects can be as large as those from the H6-H6 box diagrams. Using the parameters that are constrained by the K0-K̄0 mixing parameter ΔMK and the kaon indirect CP violation ϵK, we find that the left-handed color-sextet diquark can lead to the kaon direct CP violation being Re(ϵ′/ϵ)∼0.3×10-3. In the chosen scheme, although the diquark contribution to KL→π0νν is small, the branching ratio of K+→π+νν can reach the current experimental upper bound.

Original languageEnglish
Article number115006
JournalPhysical Review D
Volume99
Issue number11
DOIs
Publication statusPublished - 2019 Jun 6

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boxes
diagrams
quarks
CP violation
color
matrices
bosons
scalars

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

Cite this

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abstract = "We investigate whether a color-sextet scalar diquark (H6) coupling to the left-handed quarks contributes to the ΔS=2 process. It is found that the box diagrams mediated by W and H6 bosons have no contributions to ΔS=2 when the limit of mt=0 is used, and the flavor mixing matrices for diagonalizing quark mass matrices are introduced at the same time. When the heavy top-quark mass effects are taken into account, it is found that in addition to the W-H6 box diagrams significantly contributing to ΔS=2, their effects can be as large as those from the H6-H6 box diagrams. Using the parameters that are constrained by the K0-K̄0 mixing parameter ΔMK and the kaon indirect CP violation ϵK, we find that the left-handed color-sextet diquark can lead to the kaon direct CP violation being Re(ϵ′/ϵ)∼0.3×10-3. In the chosen scheme, although the diquark contribution to KL→π0νν is small, the branching ratio of K+→π+νν can reach the current experimental upper bound.",
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Left-handed color-sextet diquark in the kaon system. / Chen, Chuan Hung; Nomura, Takaaki.

In: Physical Review D, Vol. 99, No. 11, 115006, 06.06.2019.

Research output: Contribution to journalArticle

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AB - We investigate whether a color-sextet scalar diquark (H6) coupling to the left-handed quarks contributes to the ΔS=2 process. It is found that the box diagrams mediated by W and H6 bosons have no contributions to ΔS=2 when the limit of mt=0 is used, and the flavor mixing matrices for diagonalizing quark mass matrices are introduced at the same time. When the heavy top-quark mass effects are taken into account, it is found that in addition to the W-H6 box diagrams significantly contributing to ΔS=2, their effects can be as large as those from the H6-H6 box diagrams. Using the parameters that are constrained by the K0-K̄0 mixing parameter ΔMK and the kaon indirect CP violation ϵK, we find that the left-handed color-sextet diquark can lead to the kaon direct CP violation being Re(ϵ′/ϵ)∼0.3×10-3. In the chosen scheme, although the diquark contribution to KL→π0νν is small, the branching ratio of K+→π+νν can reach the current experimental upper bound.

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